Semiconductor integrated circuit device

ABSTRACT

A semiconductor integrated circuit device having a control signal system for avoiding failure to check an indefinite signal propagation prevention circuit, for facilitating a check included in an automated tool, and for facilitating a power shutdown control inside a chip. In the semiconductor integrated circuit device, power shutdown priorities are provided by independent power domains (Area A to Area I). A method for preventing a power domain having a lower priority from being turned OFF when a circuit having a high priority is turned ON is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 11/447,168 filedJun. 6, 2006. The present application also claims priority from Japanesepatent application No. JP 2005-166714 filed on Jun. 7, 2005, the contentof which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor integrated circuitdevice. In particular, the present invention relates to a techniqueeffectively applied to a system LSI for a portable device or amicroprocessor.

In recent years, with high integration caused by a finer semiconductormanufacturing process, an SoC (System-on-a-Chip) has been generallyknown. As such, systems integrated on an LSI are known. However, withthis finer process, a leakage current in each transistor has increasedmore and more, and a leakage current of the whole SoC chip has becomevery large. Conventionally, this leakage current has been thought to beimportant in a so-called standby state. However, this leakage current isbecoming a problem at the time of operation.

For example, in the SoC for a portable cellular phone, the circuit scalehas become tremendously large. In the future, it is expected that, inthe worst state, about 1/10 of an operating current will be occupied bya leakage current. The SoC applied to a portable cellular phone ispresumed as being driven by batteries. Moreover, because of its smallsize, its battery capacitance is limited. Thus, even at the time ofoperation, it is important to reduce this leakage current in order tohave long time operation of a cellular phone device. A technique ofusing a circuit operated at different power supplies as a relay buffer(patent document 1) is known as a conventional technique.

In order to reduce a leakage current of the SoC, there is proposed atechnique of subdividing a power domain inside of the chip, and then,selectively shutting down the power supply (patent document 2 andnon-patent document 1)

[Patent document 1] Japanese Patent Laid-open Publication No. 2003-78009

[Patent document 2] Japanese Patent Laid-open Publication No.2003-218682

[Non-patent document 1] ‘μ I/O Architecture for 0.13-μmWide-Voltage-Range System-on-Package (SoP) Design’ 2002 Symposium onVLSI circuits Digest of Technical Papers, pp. 168 to 169, June, 2002

SUMMARY OF THE INVENTION

In the foregoing SoC, there is an advantageous effect in reducing aleakage current of the SoC according to the techniques of patentdocument 2 and non-patent document 1. However, a plurality ofindependent power domains is provided inside of one chip. In the casewhere power shutdown is independently controlled, some problems occur asto the signal wiring in the chip. The problems are listed below.

1. Power shutdown variations increase in number, and an indefinitesignal propagation prevention design becomes complicated.

2. A repeater (signal amplifier circuit) must be mounted.

3. A clock signal must be distributed.

4. A backup memory for retaining information must be mounted.

First, a description will be given with respect to problem 1. In a CMOScircuit, in the case where a signal indicating 0 (ground level VSS) or 1(power supply level VDD) of a digital signal is included in an inputsection, a current called a penetration current is not generated.However, if a voltage of an intermediate value between these signals isinputted, there is a tendency that a large penetration current is fed.Thus, in the case where there is a fear that such a voltage of theintermediate value is applied, it is necessary to carry out reduction inthe penetration current by using a function called μ I/O. This can beachieved by using an AND function, for example. This is because, even inthe case where an intermediate voltage has been inputted to one input ofthis AND function, the other input is set at VSS, thereby making itpossible to reduce the penetration current and guarantee a Lo level at acircuit at a later stage.

In order to design independent power shutdown areas inside of an LSI,there is a need to assume that a signal outputted from the powershutdown area outputs an intermediate value, and a need to takenecessary steps to avoid an influence of the intermediate value. In thecase where there exists a plurality of independent power shutdown areasand power shutdown control is carried out in these areas independently,the above described penetration current preventing measure must be takenwith respect to a signal passing from each of the power domains toanother power domain. A current general design flow is divided into alogic design for designing a circuit function and a layout design foractually laying out a result of the design. This penetration currentproof measure must be taken between these two design flows. If there area plurality of variations, the control method becomes complicated. Thus,there is a fear that a design is not finished within a limited designingperiod.

A description will be given with respect to problem 2. An SoC chip isvery large in circuit scale. Therefore, there is a tendency that a chipalso becomes large in size. In such an SoC, for example, considering acase in which a signal from a center part of the chip is directlytransmitted to the outside of the chip, a resistance (R) and acapacitance (C) of a wiring become large, respectively. Thus, a timeconstant of a signal represented by a product thereof becomes large, atransmission delay is degraded, and an unsharpened signal waveform isgenerated. If this unsharpened signal is inputted to a circuit receivingthat signal, a large penetration current flows through that circuit.Thus, conventionally, an increase in signal delay and an increase inpenetration current have been avoided by incorporating a relay bufferfor amplifying a signal called a repeater, at proper intervals in orderto transmit a signal from the center part of the chip.

However, in the case where the inside of the SoC is subdivided into anumber of independent power domains, and power is independently shutdown respectively, it becomes difficult to determine how this repeateris allocated. This is because, in the case where there is an area inwhich power is shut down in the middle of signal wiring, signaltransmission stops there. In addition, problem 1 described above occursdepending on how the repeater is placed and a power shutdown state of asignal exchange block. That is, in the case where a signal from a powershutdown area is received by a repeater in an area in which power isapplied, there is a need for a circuit, such as a NAND circuit, and acontrol signal. When such a circuit is applied in accordance with thenumber of combinations of power shutdown, there is a need for a verylarge number of circuits and signals.

Further, a description will be given with respect to problem 3. Ingeneral clock distributing signals are distributed everywhere on a chipby properly carrying out buffering from a common clock generator in thechip. However, in the case where the inside of the SoC is subdividedinto a number of independent power domains, and power is shut downrespectively independently, it becomes difficult to allocate a driverfor this clock distribution. This is because, in the case where thisclock signal is transmitted to a target power domain, if there exists apower domain in which power is shut down before the target area, poweris shut down at a clock driver allocated there, thus making itimpossible to distribute the clock signal to a later stage.

Lastly, a description will be given with respect to problem 4. As one ofthe problems with carrying out power shutdown, there is a problem that aCMOS circuit information is volatized. That is, a basic data retentionmethod in a CMOS circuit is carried out by a circuit obtained byconnecting two stages of inverters to each other (hereinafter, referredto as a balloon circuit) in the simplest configuration. This circuitcannot retain internal information if no power supply is applied. Acircuit called a flip flop or a resistor file and the like can beexemplified as that having such a circuit.

In a current LSI, it is known to carry out a computing processingoperation while retaining required information in such a flip flop or aresistor file. If the data retained in these circuits is lost, all ofthe information processing states before power shutdown are lost, thusmaking it impossible to restart information processing from a statepreceding power shutdown. In order to reset this data, in general, it isnecessary to save the data obtained before power shutdown to an externalmemory by means of a processing operation of an OS or the like; at thetime of recovery from power shutdown, read out the required data againfrom that external memory or the like; and write the read out data in aflip flop or a resistor file. It is known that such a control requiresseveral milliseconds or more, thus making it difficult to achievehigh-speed recovery from power shutdown. Therefore, in order to achievehigh-speed recovery from power shutdown, it is necessary to retain aminimum required information in the vicinity of a power shutdown area atthe time of power shutdown.

Therefore, the present invention has been made to solve problems 1 to 4described above. It is an object to provide a semiconductor integratedcircuit device capable of arranging a control signal system in order toavoid a danger of failure to check an indefinite signal propagationprevention circuit or the like, further facilitating a check oriented tomounting on an automated tool, and facilitating power shutdown controlinside of a chip.

The foregoing and other objects and novel features of the presentinvention would be apparent from a description of the presentspecification and the accompanying drawings.

Of the inventions disclosed in the present application, a briefdescription of the inventions is as follows.

According to the present invention, power shutdown priorities areprovided by independent power domains (functional blocks); and a rule isprovided, the rule defining that, in the case where a circuit having ahigh priority is turned ON, power cannot be turned OFF in a power domainhaving a lower priority, facilitating a designing method.

In addition, according to the present invention, areas capable ofapplying still another power supply are provided in the independentpower domains, and a relay buffer (repeater) and a clock buffer or aninformation retaining latch for saving information are integrated in theareas. A layout may be correctively provided in a direction vertical toa direction in which cells are arranged in a row direction for thepurpose of dispersing a current of a power supply line.

Specifically, the present invention is applied to a semiconductorintegrated circuit device comprising a first power supply and first,second, and M+1-th functional blocks that are operated by second, third,and M-th power supplies different from power supplies for use in thefirst power supply and other functional blocks, respectively, whereinthe first to M-th functional blocks are integrated on one chip. Thepresent invention has the following features:

The second to M+1-th power supplies have power supplies independent fromeach other. In the first to M-th functional blocks, control of powershutdown can be independently achieved, and the power shutdownpriorities are assigned respectively. The priorities are determineddepending on operation and linkage specification of the functionalblocks. In the functional blocks, hierarchies are defined in accordancewith the priorities. Signal wiring relationships between functionalblocks are associated with each other based on the priorities, and arehierarchically defined before carrying out the signal wiring. From amongthe first to M-th functional blocks, between J-th and K-th functionalblocks located in the lower hierarchy and an L-th functional blocklocated in the upper hierarchy of the J-th and M-th functional blocks,when exchange of a signal from the J-th functional block to the K-thfunctional block is carried out, the signal is transmitted via a signalrelay buffer circuit provided inside of an L-th functional block. When asignal is transmitted from the J-th functional block to the L-thfunctional block, the signal is transmitted via an indefinite signalpropagation prevention circuit. When a signal is transmitted from theL-th functional block to the K-th functional block, the indefinitesignal propagation prevention circuit is eliminated.

The functional blocks in the upper hierarchy are provided inside of thefunctional blocks in the lower hierarchy. A layout of the functionalblocks in the upper hierarchy provided in the functional blocks in thislower hierarchy is laid out so that a plurality of circuit cells areprovided in a direction vertical to that of the power supply wiring inthe lowest layer that is the power supply wiring of basic circuit cells.The power supplies of the functional blocks in the upper hierarchy arewired in a meshed shape inside of a chip so that a drop of a powervoltage is minimized in the power supplies of the functional blocks inthe lower hierarchy.

In addition, the present invention is applied to a semiconductorintegrated circuit device, the device comprising: a power switchcomposed of a second gate insulating film having a thickness which isgreater than a gate insulating film thickness of a first MISFET thatconfigures a logic circuit; and a power switch controller composed of aMISFET having the second gate insulating film thickness. The presentinvention has the following feature:

The power switch controller first turns ON a small sized first powerswitch, and then, turns ON a large sized second power switch. Thepresent invention is characterized in that, when control of the powerswitch is achieved to be turned ON/OFF, there are provided: a sensorcircuit for detecting a voltage level of a virtual ground power supplyand a sensor circuit for detecting a voltage level of a gate signal ofthe power switch.

In addition, another embodiment of a power switch controller ischaracterized in that an ON/OFF control is carried out by using onelarge sized power switch, and the control is carried out by controllinga gate signal of the power switch while switching a plurality of largeand small driving drivers. Upon control of gate signals of these powerswitches, in order to minimize a deviation from a preset value, thepresent invention is characterized in that a signal at a distal end ofthe gate signals of the power switches is monitored, thereby controllingthe power switches with high precision.

The sensor circuits used during control of these power switches serve asa dynamic comparator circuit for generating a clock signal inside of thepower switch controller, and then, dynamically starting up a senseamplifier by using the generated clock signal.

In addition, the present invention is applied to a semiconductorintegrated circuit device, the device comprising a circuit formonitoring an oscillation frequency of a ring oscillator, and observinga fluctuation of an internal power voltage.

Advantageous effects attained by the present invention will be describedas follows:

According to the present invention, there is attained an advantageouseffect that power shutdown priorities are determined as a design ofpower domains of an SoC in which there exist a plurality of areas inwhich power is shut down independently, and power shutdown areas arehierarchically defined, thereby making it possible to arrange a controlsignal system and avoid a danger of failure to check an indefinitesignal propagation prevention circuit or the like. Further, there isalso attained an advantageous effect that ruled power shutdown isprovided, thereby facilitating a check oriented to mounting on anautomated tool.

In addition, according to the present invention, there is attained anadvantageous effect that, in one power domain, a power supply blockother than the power supply in the area is provided; the provided blockis laid out in a direction vertical to power supply wiring in the lowestlayer for supplying power to standard cells; this area is defined as anarea having a low power supply priority; and a relay buffer and a clockbuffer or an information retaining latch at the time of power shutdownare mounted in that area, thereby making it possible to facilitate powershutdown control inside of a chip.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practicing the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an example of a hierarchy in an independentpower shutdown area in a first embodiment relating to a semiconductorintegrated circuit device according to the present invention;

FIG. 2 is a view showing an example of signal exchange betweenindependent power shutdown areas in the first embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 3 is a view showing another example of signal exchange betweenindependent power shutdown areas in the first embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 4 is a view showing still another example of signal exchangebetween independent power shutdown areas in the first embodimentrelating to the semiconductor integrated circuit device according to thepresent invention;

FIG. 5 is a view showing yet another example of signal exchange betweenindependent power shutdown areas in the first embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 6 is a view showing an example in the case where an independentpower shutdown area is mounted on a chip in a second embodiment relatingto a semiconductor integrated circuit device according to the presentinvention;

FIG. 7 is a view showing another example in the case where anindependent power shutdown area is mounted on a chip in the secondembodiment relating to the semiconductor integrated circuit deviceaccording to the present invention;

FIG. 8 is a view showing an example of a subsidiary power domain in athird embodiment relating to a semiconductor integrated circuit deviceaccording to the present invention;

FIG. 9A is a view showing an example of illustration of a power supplyterminal of a constituent circuit in the third embodiment relating tothe semiconductor integrated circuit device according to the presentinvention;

FIG. 9B is a view showing an example of illustration of a power supplyterminal of a constituent circuit in the third embodiment relating tothe semiconductor integrated circuit device according to the presentinvention;

FIG. 10 is a view showing an example of a layout of a subsidiary powerdomain in a fourth embodiment relating to a semiconductor integratedcircuit device according to the present invention;

FIG. 11A is a view showing an example of a cross section in the vicinityof the subsidiary power domain in the fourth embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 11B is a view showing an example of a cross section in the vicinityof the subsidiary power domain in the fourth embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 12 is a view showing an example of connection between a powersupply wiring and a power switch in a fifth embodiment relating to asemiconductor integrated circuit device according to the presentinvention;

FIG. 13A is a view showing an example of a configuration in the casewhere a plurality of independent power shutdown areas exist in a sixthembodiment relating to a semiconductor integrated circuit deviceaccording to the present invention;

FIG. 13B is a view showing an example of a configuration in the casewhere a plurality of independent power shutdown areas exist in a sixthembodiment relating to a semiconductor integrated circuit deviceaccording to the present invention;

FIG. 14 is a view showing an example of a circuit configuration of astandard flip flop and an information retaining latch in a seventhembodiment relating to a semiconductor integrated circuit deviceaccording to the present invention;

FIG. 15 is a view showing an example of an operating waveform of astandard flip flop and an information retaining latch in a seventhembodiment relating to a semiconductor integrated circuit deviceaccording to the present invention;

FIG. 16 is a view showing another example of a circuit configuration ofa standard flip flop and an information retaining latch in an eighthembodiment relating to a semiconductor integrated circuit deviceaccording to the present invention;

FIG. 17A is a view showing an example of a configuration of a clockbuffer mounted in a subsidiary power domain in a ninth embodimentrelating to a semiconductor integrated circuit device according to thepresent invention;

FIG. 17B is a view showing an example of a configuration of a clockbuffer mounted in a subsidiary power domain in a ninth embodimentrelating to a semiconductor integrated circuit device according to thepresent invention;

FIG. 18 is a view showing an example of design flow of a semiconductorintegrated circuit device in a tenth embodiment relating to asemiconductor integrated circuit device according to the presentinvention;

FIG. 19 is a view showing an example of a power switch controller in aneleventh embodiment relating to a semiconductor integrated circuitdevice according to the present invention;

FIG. 20A is a view showing an example of a sensor circuit in theeleventh embodiment of the semiconductor integrated circuit deviceaccording to the present invention;

FIG. 20B is a view showing an example of a sensor circuit in theeleventh embodiment of the semiconductor integrated circuit deviceaccording to the present invention;

FIG. 21A is a view showing an example of an operating waveform of adynamic comparator in the eleventh embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 21B is a view showing an example of an operating waveform of adynamic comparator in the eleventh embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 22 is a view showing an example of an operating waveform of a powerswitch controller in the eleventh embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 23 is a view showing another example of a power switch controllerin a twelfth embodiment relating to the semiconductor integrated circuitdevice according to the present invention;

FIG. 24 is a view showing an example of a connection relationshipbetween a power switch controller and a power switch in the twelfthembodiment relating to the semiconductor integrated circuit deviceaccording to the present invention;

FIG. 25 is a view showing an example of an operating waveform of a powerswitch controller in the twelfth embodiment relating to thesemiconductor integrated circuit device according to the presentinvention;

FIG. 26A is a view showing an example of a voltage monitor circuit in athirteenth embodiment relating to a semiconductor integrated circuitdevice according to the present invention;

FIG. 26B is a view showing an example of a voltage monitor circuit in athirteenth embodiment relating to a semiconductor integrated circuitdevice according to the present invention;

FIG. 27 is a view showing an example in the case where a configurationof a power supply separating area is mounted on a chip in a fourteenthembodiment relating to a semiconductor integrated circuit deviceaccording to the present invention; and

FIG. 28 is a view showing an example where a configuration of a powersupply separating area is mounted on a chip in a fifteenth embodimentrelating to a semiconductor integrated circuit device according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. In allthe drawings for illustrating embodiments, like constituent elements aredesignated by like reference numerals. A duplicate description isomitted. In addition, constituent elements and signal names configuringa semiconductor integrated circuit device will be occasionally describedby using only signs assigned thereto.

In the following description, a power domain used here is referred to asa functional block. This functional block designates a blockindividually having a function such as a baseband processor, anapplication processor, and a memory.

First Embodiment

With reference to FIG. 1 to FIG. 5, a description will be given withrespect to a first embodiment relating to a semiconductor integratedcircuit device according to the present invention.

FIG. 1 is a view showing a method for configuring power domains withrespect to a case in which four power domain hierarchies and nineindependent power domains are assumed to exist inside of an SoC as anexample of a hierarchy of independent power interrupt areas. Theseindependent power domains are operated by a high voltage power supplyand a ground power supply that is different from the high voltage powersupply and a power supply used in other power domains, and therespectively different ground power supplies are supplied independentlyof each other. In addition, in these power domains, control of powershutdown can be achieved independently from each other; the powershutdown priorities are assigned respectively; the priorities areassociated with each other based on a relationship between signalwirings; and the signal wirings are hierarchically carried out.

While FIG. 1 describes power domains Area A to Area I by power supplyhierarchies PHD1 to PDH4, the upper priority is assigned to a powerdomain having a low power shutdown priority, and the power shutdownpriority becomes higher as the hierarchy goes to the lower layer. Here,a lower priority is referred to as a “parent”, and a higher priority isreferred to as a “child”.

In addition, a relationship between the “parent” and the “child” dependson a relationship between signal wirings. The arrow shown in the figureindicates a signal exchange relationship. For example, while the“parent” of Area A and Area B is Area C, Area G cannot be the “parent”of Area A and Area B. To the “parent”, while power is applied to the“child”, power is always applied continuously. Therefore, in signalwiring between power supply domains, even if power is shut down in the“child”, indefinite propagation prevention control of a signal line canbe carried out via the “parent”. In this indefinite propagationprevention function, for example, control of an indefinite propagationprevention control signal may be achieved via the “parent” by applying acircuit technique (μ I/O) described in the non-patent document 1, forexample.

A method for shutting down power will be described by way of an example.First, assume a case in which communication is required in Area A andArea B. In this case, communication is made between Area A and Area Bvia Area C that falls in the “parent”. Next, assume a case in whichcommunication is required between Area A and Area D. In this case, asignal from Area A may be processed so as to be transmitted to Area Dvia Area C that falls in the “parent” of Area A and Area H that falls inthe “parent” of Area C, and then, via Area G that falls in the “parent”of Area D.

FIG. 2 is a view specifically showing a case in which signaltransmission from Area A and area D occurs as an example of signalexchange between independent power shutdown areas. A path of this signaltransmission is composed of a signal SIG1 from Area A to Area C; asignal SIG2 from Area C to Area H; a signal SIG3 from Area H to Area G;and a signal SIG4 from Area G to Area D.

In this way, in the case where communication between two areas istransmitted across a plurality of power domains, it is necessary toprovide an indefinite signal propagation prevention circuit. It isnecessary to install this indefinite signal propagation preventioncircuit to an input section of a signal transmitted from the “child”side to the “parent” side. It is not necessary to insert an indefinitesignal propagation prevention circuit on a signal transmission path fromthe “parent” side to the “child” side. This is because, when a powershutdown control system according to the present invention is used, inthe case where the power is shut down at the “child” side, the powersupply at the “parent” side may be applied, and in the case where poweris applied at the “child” side, also the power supply at the “parent”side is always applied.

In the example shown in FIG. 2, indefinite signal propagation preventioncircuits MIO1 and MIO2 may be provided, respectively, at an inputsection of Area C of a signal transmitted from Area A to Area C and atan input section of Area H of a signal transmitted from Area C to AreaH. A control of control signals of the respective indefinite signalpropagation prevention circuits are achieved by means of control signalsfrom power domains in which these circuits are included. A control ofMIO1 is achieved by means of a control signal CTL1 from Area C and acontrol of MIO2 is achieved by means of a control signal CTL2 from AreaH. The control signals of these indefinite signal propagation preventioncircuits are generated in Area C and Area H.

FIG. 3 shows another example of signal transmission from Area A to AreaD, as an example of signal exchange between independent power shutdownareas. A path of this signal transmission is composed of a signal SIG1from Area A to Area C; a signal SIG2 from Area C to Area H; a signalSIG3 from Area H to Area G; and a signal SIG4 from Area G to Area D.

In the example shown in FIG. 3, an indefinite signal propagationprevention circuit may be provided as in FIG. 2. Namely, with respect toa signal to be transmitted from Area A to Area C, and a signal to betransmitted from Area C to Area H, indefinite signal propagationprevention circuits MIO1 and MIO2 may be provided at an input section ofArea C and an input section of Area H, respectively. The control signalof each indefinite signal propagation prevention circuit is controlledby means of a control signal from a power domain in which the circuit isincluded. MIO1 is controlled by means of CTL1 from Area C, and MIO2 iscontrolled by means of CTL2 from Area H.

A difference from FIG. 2 is that the control signals of these indefinitesignal propagation prevention circuits are controlled by means of acontrol signal from a block for integrally controlling a SoC (assumingthat the control signals are provided in Area I) instead of beinggenerated in Area C and Area H. In that case, a control signal istransmitted to Area H by means of CTL3, and that signal is divided intoCTL2 and CTL4. CTL4 is further transmitted to Area C in the lower layer,and CTL1 is controlled. CTL1, CTL2, and CTL4 may be the same signallines as CTL3. That is, with respect to these signal lines, a driveforce is merely amplified and transmitted by means of a buffer circuitin Area H and Area C.

In addition, CTL1, CTL2, and CTL4 may be provided as signals, each ofwhich is different from CTL3. That is, a control of CTL2 and CTL4 may beachieved after being logically computed in Area H. In this case, Area Hcan control CTL2 or CTL4 by using other conditions other than CTL3, suchas, for example, information contained inside of Area H. Similarly, AreaC can control CTL1 by using the information contained in Area C as wellas the information on CTL4.

FIG. 4 shows still another example of a signal transmission from Area Ato Area D, as an example of signal exchange between independent powershutdown areas. A path of this signal transmission is composed of asignal SIG5 from Area A to Area H and a signal SIG6 from Area H to AreaD.

In the example shown in FIG. 4, an indefinite signal propagationprevention circuit MIO2 is provided at an input section of Area H of asignal transmitted from Area A to Area H. A control of the controlsignals of the respective indefinite signal propagation preventioncircuits is achieved by means of control signals from power domains inwhich the circuits are included. A control of MIO2 is achieved by meansof a control signal CTL2 from Area H.

The control signals of these indefinite signal propagation preventioncircuits may be generated in Area H or may be generated in Area I. Theembodiment can also be carried out in accordance with the method similarto those shown in FIG. 2 and FIG. 3. This embodiment shows that, in thecase where there is a hierarchical structure of power shutdown as shownin FIG. 4, a connection can be made even if a signal is not transmittedvia an intermediate hierarchy. In this case, it is through Area Gprovided between Area H and Area D as a physical (layout based)allocation. Transmission of a signal via Area G may contribute toimprovement of signal quality. In that case, a signal can be transmittedvia Area G, as shown in FIG. 2 and FIG. 3.

FIG. 5 shows still another example of a signal transmission from Area Ato Area D, as an example of signal exchange between independent powershutdown areas. Routing of this signal transmission is carried out bymeans of a signal SIG7 from, Area A to Area D.

In the example shown in FIG. 5, an indefinite signal propagationprevention circuit MIO3 is provided at an input section of Area D of asignal transmitted from Area A to Area D. A control of the controlsignals of the respective indefinite signal propagation preventioncircuits is achieved by means of control signals from power domains inwhich the circuits are included. A control of MIO3 is achieved by meansof a control signal CTL7 from Area D. What is emphasized here is that,even if a signal is not actually transmitted via a parent hierarchy, acontrol signal is actually transmitted via only the upper hierarchy froma functional block associated with communication, whereby a design ofthe indefinite signal propagation prevention circuit cannot befacilitated. According to the present invention, there is established arule that, in the case where another functional block exists betweenfunctional blocks in which communication is required, and such afunctional block has a relationship as a “child” to a functional blockassociated with communication, the communication is not made via thatblock. In the case where repeater wiring is physically mandatory,communication is carried out via a subsidiary power domain having alower power shutdown priority, described later in detail.

The control signals of these indefinite signal propagation preventioncircuits may be signals generated in Area D or signals (CTL3-CTL5-CTL6)which are generated in Area I and transmitted to Area D via Area H andArea G. The embodiment can be carried out basically in accordance withthe method similar to those shown in FIG. 2 and FIG. 3. This embodimentshows that, in the case where there is a hierarchical structure of powershutdown as shown in FIG. 5 as well, connection can be made even if asignal is not transmitted via an intermediate hierarchy.

Signal transmission from Area A to Area D has been described withreference to FIGS. 2-5. A method for transmitting a signal from Area Ato Area D has been described by way of a variety of examples. This isdue to physical allocation of Area A and Area D. In the case where AreaA and Area D are very distant from each other, it is desirable that asignal to be transmitted via each hierarchy, as shown in FIG. 2 and FIG.3. However, in the case where Area A and Area D are allocated inproximity to each other, signal connection described in FIG. 4 or FIG. 5is effective in order to reduce signal wiring to the minimum.

Up to now, a description has been given with respect to a designingsystem in SoC power domains including a plurality of areas in whichpower is shut down independently. As described above, there is attainedan advantageous effect that a rank of facility of power shutdown isdetermined, and power shutdown areas are hierarchically defined, wherebya control signal system is arranged, and a danger of failure to check anindefinite signal propagation prevention circuit or the like can beavoided. In addition, by providing ruled power shutdown, there isattained an advantageous effect that a check oriented to mounting on anautomated tool is facilitated.

Second Embodiment

With reference to FIG. 6 and FIG. 7, a description will be given withrespect to a second embodiment relating to a semiconductor integratedcircuit device according to the present invention.

FIG. 6 is a view showing an example in which power domains described inFIGS. 1-5 are packaged on a SoC (System-on-Chip) as an example of a casein which independent power shutdown areas have been mounted on a chip.Here, there is shown an example of a division into nine power domainsfrom Area A to Area I shown in FIGS. 1-5. In addition, in FIG. 6, smallsized power domains indicated by SPA1 to SPA10 are defined as Area H.These small sized power domains are referred to as subsidiary powerdomains. This subsidiary power domain is provided as an independentpower domain having a low power shutdown priority, as shown in thehierarchy of FIG. 1, as is evident from the fact that the area isdefined as Area H. In these power domains, power is shut down inaccordance with a priority rank of power shutdown as described withreference to FIG. 1.

In FIG. 6, PSW shows a power switch, and PSWC shows a power switchcontroller. In this SoC, it is assumed that power is shut down in areasother than Area I by means of a power switch. Basically, power supply ofan internal circuit section is shut down by shutting down a power switchlocated at both sides of each power domain. While, the illustration isan example of providing a power switch only at one side, in Area B, itis to be understood that this invention is directed also to a circuitblock having small current consumption density such as an SRAM memory. Asupply current may be small in such a circuit so that the size of apower switch can be reduced.

While subsidiary power domains SPA1 to SPA10 serving as Area H will bedescribed later in detail, power shutdown control is carried out bycontrolling the ON/OFF of a power switch for subsidiary power domaindesigned in advance in a power switch area of an independent powerdomain (such as Area A, for example) including the correspondingsubsidiary power domain.

A subsidiary power domain solves three problems, such as, a problem withrepeater application, a problem with clock buffer allocation, and aproblem with latch allocation for information retaining power shutdown,with respect to four problems described in the Summary of the Inventionsection. As illustrated, SPA1 to SPA10 are characterized in that powerdomains operated by other power supply are provided in areas in whichstandard cells inside of power domains are generally allocated. Further,these SPA1 to SPA10 are provided as areas extending in a y direction.Although this is described in more detail later, it is known to providea metal layer having a low resistance value and a thick wiring width inthe upper layer in a fine process LSI. In many cases, packing is carriedout by wiring that extends in an x direction of FIG. 6. Therefore, thesubsidiary power domains SPA1 to SPA10 are designed as cells that extendin the y direction, whereby wiring is provided in a meshed shape. Thereis an advantageous effect that the lowered resistance of a power supplytrunk can be achieved, and then, a voltage drop in the case wherecurrent consumption is high can be reduced to the minimum.

The subsidiary power domains are allocated so as to sparsely exist ineach power domain. This allocation is made in order to solve theabove-described three problems. First, in the case where there is a needfor signal transmission to Area D from a circuit in an area, forexample, Area A, a repeater signal must be passed through any one ofArea B, Area C, and Area E located between Area A and Area D. However,in accordance with a power shutdown rule shown in FIG. 1, first, asignal from Area A is transmitted to Area C that falls in a “parent” ofArea A. Then, the signal must be transmitted to the target Area D viaArea G that falls into a “parent” of the target power domain via Area Hthat falls into a “parent” of Area C.

A buffer circuit called a repeater can be installed in each of theseareas, and an indefinite signal propagation prevention circuit is addedas required. In the case where a signal is thus transmitted, if Area His not allocated to any one of subsidiary areas SPA1 to 4, a signal fromArea G to Area D that is a target power domain must be wired without arepeater. In such a case, a signal wiring length is increased, and aload is increased. It is expected that a signal waveform is increased.Thus, an operating speed is reduced, and a waveform is dulled, wherein apenetration current flows in an input circuit to which that waveform isto be inputted. Therefore, by handling these SPA1 to 10 as Area H, asignal line can be wired in accordance with a method described in FIG.4. As a result, reduction of signal line wiring from Area A to Area Dshown in FIG. 6 to the minimum is achieved, and quality can be improvedon all aspects such as operating speed and power consumption.

FIG. 7 shows another example of a method for allocating power domainsshown in FIG. 6 as an example of a case in which independent powershutdown areas have been mounted on a chip. A difference from FIG. 6 isthat power switch controllers are intensively allocated at one site. Itis preferable that the power switch controllers to be designed by asimilar MISFET in order to control a power switch using a MISFET havinglarge gate insulation film thickness generally used in an I/O inconsideration of a low leakage at the time of standby, and thus there isa need of a higher voltage power supply than in the internal logiccircuit. It might be difficult to wire a power supply of this highvoltage inside a SoC, because it requires revising the power wiringmethod or the tool used for the wiring. Therefore, there is attained anadvantageous effect that power supply of a high voltage is easily laidout by using the above-described allocating method.

Third Embodiment

With reference to FIG. 8 and FIG. 9, a description will be given withrespect to a third embodiment relating to a semiconductor integratedcircuit device according to the present invention.

FIG. 8 shows an example of a layout of this subsidiary power domain. InFIG. 8, wirings extending in an x direction are provided with a firstmetal layer M1, and a VDD power supply VDD and a virtual ground powersupply VSSM are wired. VSSM is provided as a power supply line that canbe shut down from a true ground by means of a power switch describedlater. Hereinafter, while the present embodiment primarily describes amethod for operating a circuit by using a virtual ground power supplyVSSM and a VDD power supply VDD connected to a VSS power supply VSS viaa switch, the present invention can be applied not only to powershutdown on such a VSS side but also to power shutdown on the VDD sidesimilarly. In addition, the present invention can also be applied to amethod for providing a power switch at both of the VDD side and VSSside.

In FIG. 8, the wiring extending in a y direction is provided with asecond metal layer M2, for example, other than a first metal layer wiredin an x direction. In FIG. 8, an area other than an area surrounded bythe dashed line indicated as SPA corresponds to a power domain, such asArea A in FIG. 6. In this area, basic circuits, each called a standardcell, inverter circuit INV, a non-conjunction circuit NAND, anon-disjunction circuit NOR, and a standard flip flop SFF are laid out.A virtual ground power supply in an area surrounded by the dashed lineindicated as SPA is provided as VSSM2, as well as a power supplyindependent from a virtual ground power supply VSSM in any other area.Thus, the present invention is characterized in that VSSM wiring that isground wiring other than that in a subsidiary power domain istemporarily terminated before the subsidiary power domain and in thatVSSM2 wiring is mounted in the same first metal layer in the subsidiarypower domain.

VDD and VSSM are globally wired in a power shutdown area other than asubsidiary power area. Thus, regular vertical trunk lines are connectedto each other, thereby reducing a resistance. An interval X2 betweenvertical trunk lines is optimally designed so as to have a voltage fallwithin a specified value when a required amount of a current is suppliedat an operating speed of an internal logic circuit.

VSSM2 wiring is provided as a power supply line for supplying power tothree circuits described in the Summary of the Invention section. Thecircuits are, a circuit of a repeater (signal amplifier circuit), aclock signal distributing buffer circuit (clock buffer), and aninformation retaining circuit for backing up data at the time of powershutdown of a power domain. This RL shown in FIG. 8 is provided as aninformation retaining latch for retaining data. This informationretaining latch RL corresponds to a specific standard flip flop out of asubsidiary power domain on a one-on-one basis. In the case where poweris shut down in an area other than a subsidiary power domain, this latchserves to save and store that data. CKBUF is provided as a clock buffercircuit for clock distribution, and RPT is provided as a repeatercircuit (relay buffer) for long distance wiring. When passing through aplurality of independent power shutdown areas, even if such passed powerdomains are shut down, these elements are provided to enable applicationof power supply.

Here, a description will be given with respect to power supplied to aMISFET, and a description with respect to a method for designing asubstrate power supply in a subsidiary power domain.

As an example, FIGS. 9A and 9B each show a power supply of a MISFET of ageneral inverter circuit. FIG. 9A, shows an example of connectinganother power supply to each of a source electrode and a substrateelectrode of an N-type MISFET and a P-type MISFET. Namely, VSS isconnected to the source electrode of the N-type MISFET, and VBN of theN-type MISFET is connected to the substrate electrode. VDD is connectedto the source electrode of one P-type MISFET, and VBP of the P-typeMISFET is connected to the substrate electrode. This type of connectionis referred to as a substrate separating type.

FIG. 9B, shows an example of connecting another power supply to each ofa source electrode and a substrate electrode of an N-type MISFET and aP-type MISFET. Namely, VSS is connected to the source electrode of theN-type MISFET. VDD is connected to the source electrode and thesubstrate electrode. This type of a connection is hereinafter referredto as a substrate integrated type.

At the time of arranging N-type MISFETs applied with different types ofpower supplies at which power shutdown is carried out independently, itis possible to easily integrate N-type MISFETs that are operated by twopower supplies by fixing substrate power supplies in a substrateseparation type circuit to a common ground. On the other hand, at thetime of arranging such N-type MISFETs with two types of independentpower supplies, in the case of a substrate integrated circuit, it isnecessary to separate the substrate power supplies in a substrate powerdomain and any other area. It is necessary to separate wells in order toseparate substrate power supplies.

FIG. 8 shows an example in which a subsidiary power domain requires awell separation area because a power shutdown mechanism caused by anN-type MISFET is assumed to be composed of a substrate integratedcircuit. In this example, it is presumed that a well separation area isprovided under a vertical power supply trunk line located at both sidesof a subsidiary power domain. The well separation area introduced herewill be described in detail in FIG. 11. In an N-type well required forwell separation, a P-type MISFET can be integrated in that area, andthis P-type MISFET can be used as a capacitance element for stabilizingpower. Therefore, this well separation area can be efficiently utilized,and there is attained an advantageous effect in overhead reduction aswell.

Fourth Embodiment

With reference to FIG. 10 and FIG. 11, a description will be given withrespect to a fourth embodiment relating to a semiconductor integratedcircuit device according to the present invention.

FIG. 10 shows an example of a layout achieving FIG. 8 as an example of alayout of subsidiary power domains. This example shows an example of thecase where a grounding power supply is shut down. While a method forshutting down a grounding power supply is described later, this methodis easily applied in the case where power is shut down at a VDD powersupply side. In that case, in consideration of a double-wellconfiguration on a P-type silicon substrate, as one of the techniquewell known by those skilled in the art, so that VDD and VSS are reread,a P-type MISFET and an N-type MISFET and a P-type well PWELL and anN-type well NWELL may be replaced respectively. Alternatively, while anarea OH is increased, even a triple-well construction can be easilyapplied so as to electrically separate a deep N-type well (DNW).

This layout assumes a layout which is provided in substrate integratedstandard cells, as shown in FIG. 9B, and it is necessary to separate anN-type MISFET in which power is to be shut down and an N-type MISFET inwhich no power is supplied. Thus, in FIG. 10, an N-type well NWELL isprovided for separating substrates of these two types of N-type MISFETsfrom each other, and two types of N-type MISFETs are laid out. A wellfor separating this substrate electric potential is an N-type well, sothat a P-type MISFET can be integrated in this area. Therefore, a P-typeMISFET is integrated as a capacitance element in this area, therebymaking it possible to efficiently utilize this area. An area other thanthis well separation area can be filled with general standard cells. Thesame standard cell library can be used in a respective one of an area inwhich the grounding power supply is VSSM and an area in which thegrounding power supply is VSSM2.

In addition, although it is not necessary to provide a well separationarea by using substrate separation type cells shown in FIG. 9A, there isa need for new wiring to provide a substrate power supply. In the casewhere a metal wiring layer can be used as one layer inside of standardcells, substrate power wiring may be carried out by using the metalwiring layer. Alternatively, in the case where such a metal wiring layercannot be used, it is possible to use a diffusion layer by producing thelayer as silicide, thereby reducing a resistance. In this case, asilicide diffusion layer is higher in resistance than metal wiring, andthus, countermeasures, such as reducing a mesh interval for reinforcingmetal wiring, may be taken.

In FIG. 10, PT1 indicates pitch intervals of vertical trunk lines, andPT2 indicates a well separating area. PT1 is provided as an area forlocating a subsidiary power domain. This area can have a width which isan integral multiple of PT2.

FIGS. 11A and 11B each show an example of a cross section taken alongthe line A-A′ and a cross section taken along the line B-B′ shown inFIG. 10 as an example of cross sections in the vicinity of a subsidiarypower domain. Although shown in the description of FIG. 10, when asubsidiary power domain is designed in substrate integrated standardcells, there is a need for well separation. FIGS. 11A and 11B each showthe well separation. FIG. 11A shows that power separation is carried outwith a P-type well area (PWA1) in which VSSM is applied to a substrateand a source and in a P-type well area (PWA2) in which VSSM2 is appliedto a substrate and a source while an N-type well area (NWA1) issandwiched therebetween. Here, a triple-well configuration isconsidered.

In the triple-well configuration used here, a deep N-type well (DNW) isdeeply produced on a P-type silicon substrate (P-sub) on which a P-typediffusion layer and an N-type diffusion layer (NL) are fabricated. Insuch a configuration, as shown in FIG. 11, the N-type well issandwiched, thereby making it possible to separate a substrate powersupply of an N-type MISFET produced in an area of the P-type well. Thismethod can minimize an area increase for separating a substrate electricpotential. Here, with respect to the area of the N-type well (NW) forcarrying out power separation, the N-type well is continuous in a ydirection, as shown in FIG. 10. Thus, this area is provided as an areain which general standard cells cannot be located. Therefore, in orderto efficiently utilize such an area, a P-type MISFET is configured inthis N-type well area, and this P-type MISFET is used as a powerstabilizing capacitance element. In this manner, there is attained anadvantageous effect that a dead space can be efficiently utilized.

In each MISFET, D denotes a drain electrode, S denotes a sourceelectrode, and G denotes a gate electrode.

FIG. 11B shows that MISFET is configured by the N-type well, in whichVDD is applied to a substrate, and a source. NWA2 and NWA 4 are ordinarystandard cell areas, and NWA3 is an area used as the well separationarea. Here, a triple-well configuration is considered. Here, NWA3 is anarea of N-type well (NW), while N-type well is continuous in a ydirection, as shown in FIG. 10. Thus, this area is provided as an areain which general standard cells cannot be located. Therefore, in orderto efficiently utilize such an area, a P-type MISFET is configured inthis N-type well area, and this P-type MISFET is used as a powerstabilizing capacitance element. In this manner, there is attained anadvantageous effect that a dead space can be efficiently utilized.

Fifth Embodiment

With reference to FIG. 12, a description will be given with respect to afifth embodiment relating to a semiconductor integrated circuit deviceaccording to the present embodiment.

FIG. 12 shows an example of a layout of power switch allocation andpower supply wiring for achieving power supply in a subsidiary powerdomain as an example of power supply wiring and power switch connection.In FIG. 12, there are provided: a circuit block CBLK that is anindependent power domain; a power switch allocation area PSWAREA forshutting down power supply of a circuit in that CBLK; and a power switchcontroller PSWC for controlling that switch. In order to reduce aresistance of a power supply line by means of the recent micro scaledLSI, there is attained an advantageous effect that the low resistance ofthe power supply line can be achieved by allocating metal wiring in theupper layer to a power supply.

FIG. 12 shows an example in which power supply wiring is provided in anx direction in the upper layer of CBLK. In that case, it is effective toprovide the metal wiring so that number of VDD power supplies, VSS powersupplies, and VSSM power supplies are as close to each other as possiblein order to achieve a low resistance of the whole power supply wiring.This wiring is composed of a metal layer having a large wiring width,and is referred to as a wide metal wiring layer (WM). Upon wiring VSSM2that is a power supply to a subsidiary power domain, there is a need forwiring a VSSM2 power supply that is a power source in a subsidiary powerdomain at a rate depending on the size of the subsidiary power domain.At this time, while maintaining a group of three power supplies of VDD,VSS, and VSSM, VSSM2 power supplies are wired at specific intervals,thus making it possible to wire a VSSM2 power supply without degrading alow resistance of a power supply wire.

The VSSM power supply and VMMS2 power supply are connected to powerswitches allocated at both sides of this power shutdown area, and theconnected power supplies are controlled by means of a control signalfrom a power switch controller. A power switch PSW1 is used forconnection between the VSSM power supply line and the VSS power supply,and a power switch PSW2 is used for connection between the VSSM2 powersupply and the VSS power supply. The respective power switches arecontrolled by means of gate drive signals g1 and g2 outputted from thepower switch controller PSWC.

Sixth Embodiment

With reference to FIG. 13A and FIG. 13B, a description will be givenwith respect to a sixth embodiment according to a semiconductorintegrated circuit device according to the present invention.

FIGS. 13A and 13B are views showing an example of arranging a powerswitch for respective independent power shutdown areas and a powerswitch for a subsidiary power domain as one example of a configurationin which a plurality of independent power shutdown areas exist.

FIG. 13A illustrates an exemplary case in which control of a powerswitch in a subsidiary power domain is also carried out independently ina power switch controller for controlling two independent power domains.It is desirable that VSSM2 power supplies serving as grounding powersupplies in a subsidiary power domain to be used in common in aplurality of power domains in order to facilitating a control operationand to achieve a low impedance of power supply wiring. In that case, itis desirable to control in common these VSSM2 power supplies by means ofa power switch controller that corresponds to each power domain on aone-on-one basis. Therefore, in FIG. 13A, it is shown control of a g2signal from power switch controllers in all areas by means of a commoncontrol signal g2ctl inputted to each power switch controller PSWC and apower switch PSW2 for shutdown control of the VSSM2 power supply.Through such a control, there is attained an advantageous effect that animpedance of power supply wiring of the VSSM2 power supply can bereduced.

FIG. 13B shows an example in which a power switch and its powercontroller in a subsidiary power domain are provided independently. Inthis way, there is attained an advantageous effect that integratedmanagement of VSSM2 of virtual ground power line in the subsidiary powerdomain in the upper wide metal wiring layer is facilitated. In thiscase, it is desirable to achieve a low resistance by wiring all of theVSSM2 power supplies with the wide metal wiring layer. A method forallocating each of VDD, VSS, VSSM, and VSSM2 with the wide metal wiringlayer may be carried out in the same manner as that shown in FIG. 13A.

Seventh Embodiment

With reference to FIGS. 14 and 15, a description will be given withrespect to a seventh embodiment of a semiconductor integrated circuitdevice according to the present invention.

FIG. 14 shows an example of circuits of a standard flip flop and aninformation retaining latch as an example of a circuit configuration ofthese constituent elements. A standard flip flop SFF is composed of:transmission gates TG1 and TG2; inverters INV1 to INV4; clockedinverters CIV1 and CIV2 or the like. This flip flop has an additionalfunction as a general parent/child type flip flop while it also has aselector SEL1 for switching a general input and an output from theinformation retaining latch RL. This SFF is provided as a circuit in anindependent power shutdown area. Thus, a ground power supply VSSM isapplied thereto. There are provided terminals of an input signal D, anoutput signal Q, and a clock signal CLK; an input signal STRD from theinformation retaining latch; and further, a selector signal RLDSEL tocontrol a selector for switching a general operation input and an inputfrom the information retaining latch. A signal from SFF to RL iscontrolled by means of an STR signal while a non-conjunction circuitNAND1 is provided partway, and, in the case where SFF data is retainedin RL, control for achieving Lo is carried out.

The information retaining latch RL mounted in a subsidiary power domainreceives save data from SFF by the clocked inverter CIV3. The receiveddata is retained by means of a latch composed of internal inverters INV5and INV6. This control is carried out by means of a data save signal STRand the inversion signal STRB. An output signal from RL is outputtedfrom an inverter INV7 by means of STRD, and the outputted signal is theninputted to a terminal of STRD from a retaining latch of SFF.

A power supply configuration of MISFFTs of these circuits will bedescribed next. In P-type MISFETs, each of source side electrodes andsubstrate electrodes is provided as VDD similarly in each of theirrespective areas. On the other hand, N-type MISFETs are different fromeach other in each area. A source electrode and a substrate electrode(grounding side power supply) of an N-type MISFET of SFF are provided asVSSM, and a source electrode and a substrate electrode (grounding powersupply) of an N-type MISFET of RL are provided as VSSM2. Here, asubstrate integrated type circuit is assumed.

FIG. 15 shows an example of operating waveforms of a standard flip flopand an information retaining latch. FIG. 15 also shows, from the top, aclock signal CLK, an input signal D to SFF, a signal of an internal nodend1, n output signal Q of SFF, an input signal STRD from RL, a signal ofa node NV to RL, a data save signal STR, a data save signal inversionsignal STRB, a selector signal RLDSEL of the input signal D, a VSSMpower supply, and a VSSM2 power supply.

First, at a time T1, a general operation of a flip flop is carried out.In this case, an input signal D is captured at a rise of a clock signalCLK; the captured signal is transmitted to an internal node nd1 as it isby means of a selector; and an output signal Q is updated and retained.

Starting a power shutdown will be described next. Prior to powershutdown, it is necessary to transfer the data in SFF to an informationretaining latch RL. In this case, a data save signal STR is set at Hi,and a data save signal inversion signal STRB is set at Lo, whereby anoutput signal Q is transmitted to a node NV via NAND for connecting theoutput signal Q to the node NV. Then, STR is set at Lo, and STRB is setat Hi, whereby signal transmission between SFF and RL is shut down, anddata is retained in RL. Then, a power shutdown switch is turned OFF at atime T3. When the power shutdown switch is turned OFF, a level of avirtual ground power supply VSSM rises, and power shutdown almostcompletes at a time T3. Although the internal data of SFF is destroyed,the data retained in RL is retained as it is.

A description will be given with respect to recovery from powershutdown. A level of a virtual ground power supply VSSM is set to 0V byturning ON a power shutdown switch at a time T4. Then, when power iscompletely turned ON at a time T5, and then, RLDSEL is set at Hi at atime T8, STRD data is transmitted to nd1. Then, nd1 data is captured ata rise of a clock, and an output signal Q is updated and retained.

Then, a general input is selected by setting RLDSEL at Lo. Subsequently,an operation for retaining an input signal D at a rise of a clock iscarried out.

Eighth Embodiment

With reference to FIG. 16, a description will be given with respect toan eighth embodiment relating to a semiconductor integrated circuitdevice according to the present invention.

FIG. 16 shows an example of a circuit configuration of an informationretaining latch other than FIG. 14 showing the information retainingcircuit provided in the subsidiary power domain. FIG. 16 shows usinggeneral flip flop FF and latch LTC registered in standard cells. Thereare provided a circuit block CB1 at a side at which power is shut downand a circuit block CB2 for retaining information by power supply in thecase where CB1 is shutdown from power supply.

CB1 is composed of: a flip flop FF for retaining information at the timeof power shutdown; a selector SEL for selecting an input signal D and aninput signal (data) STRD from CB2; a non-conjunction circuit NAND fortransmitting data to CB2; and an inverter circuit INV. CB2 is composedof a latch LTC for retaining the retained data from CB1. CB1 and CB2 canuse the same standard cells, although the grounding side powers suppliedare different from each other here. An operation of the data retainingcircuits (FF and LTC) in CB1 and CB2 is normal, and data is captured inFF in synchronism with a clock signal CLK1, and LTC at the side of CB2retains data in the case where a value of a clock signal CVLK2 is set atHi. In this way, there is attained an advantageous effect that CB1circuit power shutdown is facilitated without newly producing standardcells.

Ninth Embodiment

With reference to FIGS. 17A and 17B, a description will be given withrespect to a ninth embodiment relating to a semiconductor integratedcircuit device according to the present invention.

FIGS. 17A and 17B are views showing an example of a configuration of aclock buffer mounted in a subsidiary power domain. FIG. 17A shows aconnection configuration of a general clock distributing system. A blockbuffer is provided as a circuit for distributing clock pulses generatedfrom a clock pulse generator CPG. In general, a clock is distributed toa whole chip via some stage of these buffers. Here, there is shown anexample in which clocks are roughly distributed in four hierarchies of afirst stage clock buffer group (A-drv); a second stage clock buffergroup (B-drv); a third stage clock buffer group (C-drv); and a laststage clock buffer group (D-drv). The word “four hierarchies” used heredoes not imply distribution by four clock buffers, but implies that aclock buffer category is roughly divided into four groups. Therefore, aplurality of clock buffer can be buffered in each hierarchy. Forexample, the clock buffer A-drv can be transmitted to the clock bufferB-drv via the second stage buffer circuit.

In the case where a plurality of power shutdown areas is mounted on achip, there is a problem with how to locate a clock distributingcircuit. Here, this problem is solved by mounting in a subsidiary powerdomain some buffers in hierarchy A which serves to distribute a clock tothe whole chip. By doing so, the number of clock buffers mounted in thesubsidiary power domain can be decreased, making it possible tocontribute to leakage current reduction at the time of the chip standby.

FIG. 17B shows a modified example of FIG. 17A. In this example, a blockgating technique is applied to a buffer hierarchy provided partway. Thisexample also shows an example in which clock gating has been applied toB-drv and D-drv. An output of B-drv is fixed to Lo by setting a gatingsignal GATE1 of B-drv at Lo. When GATE1 is set at Hi, a clock signalpropagates. Similarly, an output of D-drv is fixed to Lo by setting agating signal GATE2 of D-drv at Lo. When GATE2 is set at Hi, a clocksignal propagates. A control of this gate signal must be achieved so asto be identical to that in a power supply hierarchy of a power domain inwhich a clock buffer is mounted or must be achieved through the upperpower supply hierarchy. Otherwise, there is a danger that a penetrationcurrent is generated at a clock gating circuit.

Tenth Embodiment

With reference to FIG. 18, a description will be given with respect to atenth embodiment of a semiconductor integrated circuit device accordingto the present invention.

FIG. 18 is a view showing an example of a design flow of a semiconductorintegrated circuit device. This embodiment is characterized in that thestep of DFL (Design for Leakage) is newly provided. This step assumes anoperating method in which SoC to be manufactured is actually used, andcarries out a check of a leakage current quantity in the case where apower supply other than a portion required for operation is shut down. Aleakage current is evaluated in this step assuming a use scene, andreasonability for allocation of a power supply domain is considered.

By incorporating such a step, a plurality of independent power supplydomains in a chip is provided, thereby making it possible to design aleakage current quantity. In order to carry out this step, cooperationof a front end (logic design and timing electric power evaluation) and aback end (layout design, DFT (Design for Test), and timing electricpower evaluation) becomes more important than those of the prior steps.This is because it is necessary to fully consider whether or not logicspecification discussed at the front end conforms to electric powerspecification required from customers, and at the same time, physicalallocation information (such as power supply domain allocation or signalline repeater allocation) is important.

In the case where the evaluated leakage current exceeds a target value,power supply domain reconfiguration is carried out, and a network changeor the like is fed back to a logic design based on a result of thatevaluation. In this manner, in consideration of a total leakage currentquantity of a chip, it becomes possible to make a design while checkingwhether or not the leakage current quantity is within the specification.

Eleventh Embodiment

With reference to FIGS. 19-22, a description will be given with respectto an eleventh embodiment relating to a semiconductor integrated circuitaccording to the present invention.

FIG. 19 is a view showing an example of a power switch controller. Thispower switch controller is composed of a MISFET having large gateinsulating film thickness used in I/O, and an operating power supplyoperated by means of VCC (3.3V, for example) and VSS. This is becausethis MISFET is designed so a to be operated by means of a high VCC powersupply as compared with a VDD power supply, thus making it possible toincrease setting of a threshold value and to reduce a sub-thresholdleakage current. Further, there is attained an advantageous effect thatgate insulating film thickness is large, thus making it possible toreduce a gate tunnel leakage current.

This power switch controller PSWC1 is composed of: a control logiccircuit CLG; a finite state machine FSM; a sensor circuit SENS10VSS of aVSSM level; a sensor circuit SENS90VCC of a gate signal level of a powerswitch; a level converter circuit LVL_DN for generating a micro I/Ocontrol signal; and a small sized power switch. SENS10VSS is driven bymeans of a control signal SONVSS, and transmits a detection completionsignal C10VSS at a time point at which a VSSM level is set at 10% VDD.SESN90VDD is driven by means of a control signal SONVSCC and transmits adetection completion signal C90VCC at a time point at which a level of agate signal G of a power switch is set at 90% VCC. In FSM, based oninformation from each sensor circuit, control of a power switch iscarried out. While CLG carries out control of a micro I/O, this microI/O is composed of a MISFET having a thin gate insulating film which isoperated by means of a VDD power supply and a VSS power supply. Thus, asignal CDN of a VCC amplitude is converted into a micro I/O controlsignal CDNMIO through a level converter circuit, and the convertedsignal is outputted.

A synchronizing type comparator synchronized with a clock signal is usedfor each sensor circuit of a voltage level. Thus, this voltage sensorsenses a voltage level while dynamically repeating clock supply from FSMto each voltage sensor and a comparison with a pre-charge by means of aclock signal. This clock may be oscillated inside of FSM by using a ringoscillator or the like.

This power switch controller PSWC1 operates an internal control circuitand drives a power switch when the controller has received a requestsignal REQ. A method for controlling the power switch uses a two-stageswitch size switching type of switching and driving a small size powerswitch and a large size power switch. In this way, a mass current calledan inrush current for electrically discharging a VSSM level can bereduced. In this system, the small size switch functions as a switch forfeeding an inrush current at the time of electrically discharging a VSSMlevel, thus making it possible to restrict the inrush current byproperly selecting the size of this power switch.

Now, a description of an operation will be given here. First, when arequest signal REQ is inputted, a control logic circuit CLG transmits astartup signal to a finite state machine FSM. This FSM transmits a stateof a power switch by means of a signal ST based on sense signals from asensor circuit SENS10VSS for measuring a voltage level of a virtualpower supply line VSSM and a sensor circuit SENS90VCC for measuring avoltage level of a gate signal G of a power switch. In the case wherethat ST indicates a state of driving, a large size switch CLG startsdriving a large size driver C1. Further, when SENS90VCC detects that agate signal G of a power switch exceeds 90% VCC, FSM moves to a state inwhich power has been turned ON. In the case where there is indicated astate in which a power switch has been turned ON by means of a signal STfrom FSM, CLG transmits an acknowledge signal ACK. Note that, in orderto initialize FSM and so on, a reset signal RES is provided, therebymaking it possible to achieve a stable operation.

FIGS. 20A and 20B show an example of a sensor circuit for detecting avoltage level of the power switch controller described in FIG. 19. FIG.20A shows a circuit for detecting a VSSM electric potential, and FIG.20B shows a circuit for detecting a voltage level of a gate signal G ofa power switch. These circuits are provided as circuits for detecting avoltage level in synchronism with a clock signal outputted from FSM,each of which is referred to as a dynamic comparator.

The sensor circuit shown in FIG. 20A will be described here. Thiscircuit is provided as a circuit for monitoring a voltage level of VSSM,and detecting the monitored level to be obtained as 10% of VDD. Thiscircuit is composed of a sense amplifier SA1, a pre-charge circuit PCH1,and a reference voltage generator circuit REFC1. When a control signalSONVSS is set at Hi, a clock is supplied to SA1 and PCH1 and VREF1 isoutputted from a circuit of REFC1. In SA1, VREF1 and VSSM targeted forevaluation are entered, and a clock signal CLK is set at Lo, a P-typeMISFET that is a power supply of a sense amplifier is turned OFF, andPCH1 carries out pre-charge. During a period in which the senseamplifier is set at Hi, the P-type MISFET that is a power supply of thesense amplifier is turned ON, and the sense amplifier is started up. Theoutput nodes ND21 and ND22 change in accordance with values of VREF1 andVSSM. In the case where VSSM>VREF1, ND22 is set at Hi, and ND21 is setat Lo. On the other hand, in the case of VSSM<VREF1, ND22 is set at Lo,and ND21 is set at Hi.

VREF1 takes a method for outputting a value obtained as 10% of VDD byresistance division. This is the simplest system. This circuit consumescurrent while a value obtained as 10% of VDD is outputted as VREF1.However, when SONVSS is set at Lo, a power switch is turned OFF by meansof a P-type MISFET (MP21) provided at the side of VDD of this resistancedivision. Therefore, in the case where this dynamic comparator does notoperate, it is possible to reduce current consumption. In this example,while power supply of a VREF1 generator circuit due to resistancedivision is controlled by means of MP21, this control is mandatory inorder to avoid malfunction because VSSM rises to the side of VDD at thetime of power shutdown. Namely, in the case where MP21 is shut down, avoltage level of VREF1 becomes infinitely close to the side of VSS. Thisis because a resistance value used here is as much as 1 kΩ at most, and,in MP21, a voltage level is obtained as a value determined by resistancedivision when it's ON, and the resistance has a value of as much as 100Ω which is smaller by one digit. When the thus designed MP21 is switchedOFF, its resistance value is increased by nine digits. Upon comparisonwith a resistance of 1 kΩ, it is possible to consider an almostinfinitely large resistance value. Thus, a value of VREF1 in the casewhere MP21 is turned OFF is very close to VSS. Therefore, in the casewhere an attempt is made to detect a level of VSSM, thereby operatingthis dynamic comparator, VREF1 shifts from VSS to 10% of VDD, and a VSSMlevel starts transition from the vicinity of VDD, thus making itpossible to detect a desired value obtained as 10% of VDD withoutcausing a malfunction.

The sensor circuit shown in FIG. 20B will be described next. Thiscircuit is provided as a circuit for monitoring a voltage level of agate signal G of a power switch, and detecting the monitored voltagelevel to be 90% of VCC. This circuit is composed of a sense amplifiercircuit SA2, a pre-charge circuit PCH2, and a reference voltagegenerator circuit REFC2. When a control signal SONVCC is set at Hi, aclock is supplied to SA2 and PCH2 and VREF2 is outputted from a circuitof REFC2. In SA2, when this VREF2 and G targeted for evaluation areentered, and a clock signal CLK is set at Lo, a P-MISFET that is a powersupply of a sense amplifier is turned OFF, then the PCH2 carries outpre-charge. On the other hand, during a period in which a clock signalis Hi, the P-type MISFET that is the power supply of the sense amplifieris turned ON, and the sense amplifier is started up. The output nodesND23 and ND24 change in accordance with values of VREF2 and G. In thecase of G<VREF2, ND24 is set at Hi, and ND23 is set at Lo. On the otherhand, in the case where G>VREF2, ND24 is set at Lo, and ND23 is set atHi.

VREF2 uses a method for outputting a value obtained as 90% of VCC byresistance division. This is the simplest system. This circuit consumesa current while a value obtained as 90% of VCC is outputted as VREF2.However, when SONVCC is set at Lo, a power switch is turned OFF by meansof an N-type MISFET (MN21) provided at the side of VSS of thisresistance division. Therefore, in the case where this dynamiccomparator does not operate, it is possible to reduce currentconsumption. In this example, power supply of a VREF2 generator circuitdue to resistance division is controlled by means of MN21. However, thiscontrol is mandatory in order to avoid a malfunction because G is fixedto the side of VSS at the time of power shutdown. Namely, a voltagelevel of VREF2 is infinitely close to the side of VCC in the case whereMN21 is shut down. This is because the resistance value used here is asmuch as 1 kΩ at most, and, in MN21, a voltage level is obtained as avalue determined by resistance division by setting its ON resistance asa value of as much as 100Ω which is smaller by one digit. When the thusdesigned MN21 is switched OFF, its resistance value is greater by ninedigits. Upon comparison with a resistance of 1 kΩ, it is possible toconsider an almost indefinitely large resistance value. Thus, a value ofVREF2 in the case where MN21 is turned OFF becomes very close to VCC.Therefore, in the case where an attempt is made to detect a level of G,thereby operating this dynamic comparator, VREF2 shifts from VCC to 90%of VCC, and the G level starts the transition from VSS, thus making itpossible to detect a desired value obtained as 90% of VCC withoutcausing a malfunction.

FIGS. 21A and 21B are views showing an example of an operating waveformof the dynamic comparator shown in FIG. 20. First, a description will begiven with respect to FIG. 21A. First, when SONVSS is set at a Hi levelat a time T1, a dynamic comparator starts operation. At this time, VREF1outputs a 10% level of VDD, and a sense amplifier starts detecting avoltage level of VSSM. An operation of the sense amplifier is insynchronism with a clock. When a clock is set at a Hi level, values ofND21 and ND22 are compared with each other. During a period in which aclock is set at Lo, a pre-charge circuit operates, and the values ofND21 and ND22 are pre-charged by means of VCC. At a time T2, a clock isset at a Hi level. As a result, the sense amplifier is started up, ND21is set at a Hi level, and ND22 is set at a Lo level. This state isestablished as a state in which a voltage level of VSSM is not equal toor smaller than 10% of VDD. During this period as well, an operation ofturning ON the power switch is carried out, and thus, the VSSM level iscontinuously driven toward the side of VSS. There is shown a case inwhich, at a time T3, the VSSM level is set to be equal to or smallerthan 10% of VDD across VREF1. At this time, in level evaluation by anext sense amplifier, ND21 is set at a Lo level, and ND22 is set at a Hilevel. As a result, C10VSS is set at a Hi level, and because VSSM leveldetection has terminated, is transmitted to FSM. In this manner, SONVSSis controlled at a Lo level from FSM, and an operation of the dynamiccomparator is terminated.

Next, a description will be given with respect to FIG. 21B. First, whenSONVCC is set at a Hi level at a time T1, a dynamic comparator startsoperation. At this time, VREF2 outputs a level of 90% of VCC, and asense amplifier starts detecting a voltage level of G. An operation ofthe sense amplifier is in synchronism with a clock. When a clock is setat a Hi level, values of ND23 and ND24 are compared with each other.During a period in which a clock is set at Lo, a pre-charge circuitoperates, and the values of ND23 and ND24 are pre-charged by means ofVCC. At a time T2, a clock is set at a Hi level. Thus, the senseamplifier is started up, ND23 is set at a Hi level, and ND24 is set at aLo level. This state is established as a state in which a VSSM level isnot equal to or greater than 90% of VCC yet. During this period as well,an operation of turning ON a power switch is carried out. Thus, avoltage level of G is continuously driven toward the side of VCC. Thereis shown a case in which a voltage level of G is equal to or greaterthan 90% of VCC across VREF2 at a time T3. At this time, in levelevaluation by a next sense amplifier, ND23 is set at a Lo level, andND24 is set at a Hi level. As a result, C90VCC is set at a Hi level, andbecause VSSM level detection has terminated, is transmitted to FSM. Inthis manner, SONVCC is controlled at a Lo level from FSM, and anoperation of the dynamic comparator terminates.

FIG. 22 shows an example of an operating waveform of a power switchcontroller described in FIG. 19. FIG. 22 shows a period (T0 state) inwhich a power switch is turned OFF; a transition period (T1 state or T2state) for turning ON a power switch; and a period (T3 state) in which apower switch is tuned ON.

First, a request signal REQ is set at Hi, whereby a power switch OFFstate T0 moves to a transition period T1 state. At this time, a gatesignal GSMAL of a small size power switch is driven so as to move fromLo to Hi, and then, to set an electric potential of VSSM at a groundlevel 0V. A SENS10VSS circuit detects a VSSM level to be 10% VDD, forexample; transmits a C10VSS signal to FSM in the case where the VSSMlevel is lower than 10% VDD; and stops operation of the sensor circuit.Having received the C10VSS signal, FSM moves a current state to a T2state immediately, and transits the result to CLG, thereby driving agate signal G of a large size driver.

This voltage level of G is sensed by means of SENS90VCC. The SENS90VCCdetects a level of G to be 90% VCC, for example, stops a SENS90VCCcircuit, and transmits C90VCC to FSM. Having received C90VCC, FSM movesa current state to a T3 state, and transmits the result to CLG. The CLGreceives the result, and transmits an ACK signal.

This power switch controller carries out control of the micro (μ) I/Odescribed in the patent document 2 mentioned above. The micro I/O is acircuit for restricting a penetration current generated in an input sidecircuit under the influence in the case where a signal value is obtainedas an indefinite value at the time of power shutdown in signal exchangedbetween a plurality of power shutdown areas. This micro I/O is providedas an AND circuit having a signal amplitude level converting function asrequired.

A control signal of this micro I/O circuit is made to be equal to orsmaller than a logical threshold value of a circuit when a VSSM level isequal to or smaller than 10% VDD. Thus, a large penetration current doesnot flow, and thus, a control for CDNMIO to be changed from Lo to Hi iscarried out at a time at which VSSM is set at 10% VDD. In this manner,in the case where ACK has been transmitted, the micro I/O can alreadyoperate, thus, making it possible to exchange a signal immediately.

Next, turning OFF a power switch will be described. First, REQ ischanged from Hi to Lo, whereby the power switch controller startsshutdown control of a power switch. In this case, the power switch isturned OFF by changing a control of a driving a current signal to Lobased on gate signals of a small size driver and a large size driver. AnACK signal and CDNMIO assume control at a time point at which REQ hasbeen entered. Control is carried out such that Lo is set, and, havingreceived REQ, a power switch is turned OFF immediately, therebydisabling use.

Twelfth Embodiment

With reference to FIGS. 23-25, a description will be given with respectto a twelfth embodiment of a semiconductor integrated circuit deviceaccording to the present invention.

FIG. 23 is a view showing another example of a power switch controller.Like the power switch controller shown in FIG. 19, this power switchcontroller is also composed of a MISFET having a large gate insulatingfilm thickness used in I/O. This switch controller is operated by meansof a VCC (for example, 3.3V) and VSS serving as operating powersupplies. This power switch controller PSWC2, unlike the example shownin FIG. 19, is characterized in that a power switch is of one type oflarge size switch, and a driver for controlling the power switch is oftwo types, a small size and large size. There is no need for limitingthe number of drivers to two. Although not shown, a control of aplurality of types of the power switches may be achieved by selectivelyusing them.

A power switch controller PSWC2 shown in FIG. 23 is composed of: acontrol logic circuit CLG; a finite state machine FSM; a sensor circuitSENS90VCC of a gate signal level of a power switch; a level convertercircuit LVL_DN for generating a micro I/O control signal; and a smallsize power switch. SESN90VCC is driven by means of a control signalSONVCC, and a detection completion signal C90VCC is transmitted at atime point at which a level of a gate signal G of the power switch isset at 90% VCC. FSM carries out control of a power switch based oninformation sent from a sensor circuit. While CLG carries out control ofa micro I/O, the micro I/O is composed of a MISFET having a small gateinsulating film that is operated by means of a VDD power supply and aVSS power supply. Thus, a signal CDN having a VCC amplitude is convertedand outputted to a micro I/O control signal CDNMIO having a VDDamplitude through a level converter circuit.

A synchronizing type comparator synchronized with a clock signal is usedfor a sensor circuit of a voltage level. Thus, this voltage sensorsenses a voltage level while dynamically repeating supply of a clockfrom FSM to the voltage sensor and comparison with pre-charge by meansof the clock signal. This clock may be oscillated inside of FSM by usinga ring oscillator or the like.

This power switch controller PSWC2 operates an internal control circuitand drives a power switch when the controller has received a requestsignal REQ. A method for controlling the power switch uses a two-stageswitch size switching type of switching and driving a small size powerswitch and a large size power switch. By doing this, a mass currentcalled an inrush current for electrically charging a VSSM level can bereduced. This system drives a gate signal of a large size power switchby means of a small size driver, thus making it possible also to slowlyset a gate of a power switch at a Hi level, and slowly turn ON a powerswitch.

At this time, a capacitance called a mirror capacitance can be generatedbetween a gate and a drain of the power switch. A gate signal of thepower switch is temporarily obtained as a constant value in order tocharge this mirror capacitance. This is a phenomenon that occurs when avoltage between a source and a drain of a small size driver has analmost constant value, and thus, this driver serves as one kind ofconstant charge supply circuit. A period in which this mirrorcapacitance is charged, is also a period in which an N-type MISFETchannel is gradually formed in a power switch, and coincides with aperiod in which VSSM is charged. At this time, a voltage of a gateelectrode is substantially equal to a threshold value of an N-typeMISFET that is a power switch. Therefore, a current supply capability ofthe power switch in this period is very weak, thus making it possible toreduce a current for charging VSSM.

Next, a description of an operation will be given. When a request signalREQ is inputted, a control logic circuit CLG transmits a startup signalto a finite state machine FSM. At this time, a small driver C0 startsdriving a gate G of a power switch. As described in FIG. 22B in detail,this FSM carries out state transition by monitoring a voltage level of anode GSEN at which a node at the most distal end side of a gate signal Gof the power switch is drawn into the power switch controller. At thisdriver C0, a plurality of drivers having a variety of driving forces areproduced in advance, thus making it possible to select a desired drivingforce. For example, utilizing the fact that, when transistors having thesame gate widths are vertically stacked, a current is halved, and whentransistors having the same gate widths are connected in parallel, acurrent is doubled, using some types of a plurality of verticallystacked drivers at stages and a plurality of drivers connected inparallel, makes it possible to achieve the invention.

A Schmidt trigger buffer SB for detecting a voltage trigger of this GSENwith rough precision and a sensor circuit SENS90VCC for measuring thedetected voltage level with high precision are provided. Based on thesense signals from the buffer and sensor, a state of a power switch istransmitted to CLG by means of a signal ST. First, upon the receipt ofan output of the Schmidt trigger buffer SB, FSM notifies CLG that alarge driver drive state is established, and, upon the receipt of thatsignal, CLG starts driving a large driver G1. Further, when FSM receivesthat a power switch has been turned ON based on a sense signal fromSENS90VCC, FSM transmits to CLG that a state in which the power has beenturned ON is established. Upon the receipt of that signal, CLG transmitsan acknowledge signal ACK. In order to initialize FSM etc., a morestable operation can be achieved by providing a reset signal RES.

FIG. 24 is a view showing an example of a connection relationship of thepower switch controller and the power switch described in FIG. 23. Acontrol signal G of the power switch connects a gate of a power switchPSW for supplying power supply to a circuit of an independent powershutdown area (CB) and connects gates of a plurality of N-type MISFETs.At this time, a node at the most distal end side is returned to a powerswitch controller PSWC2, and this is defined as GSEN. Although G andGSEN are logically the same nets, a G wiring capacitance and a wiringresistance are large, and thus, becomes a very high load. Therefore, thevalues of response to this wiring is significantly different from eachother at the distal end side and at the proximal end side depending onan RC time constant that is a product of a resistor R and a capacitor C.Thus, when a voltage is monitored at the proximal end side, there is adanger that an acknowledge signal is generated before a voltage does notrise sufficiently at the distal end side. This danger can cause amalfunction. Therefore, the danger of such a malfunction is avoided bymonitoring the distal end side.

FIG. 25 shows an example of an operating waveform of a power switchcontroller described in FIG. 23. FIG. 23 shows a period (T0 state) inwhich a power switch is turned OFF; a transition period (T1 state or T2state) for turning ON a power switch; and a period (T3 state) in which apower switch is turned ON. First, a request signal REQ is set at Hi,whereby a power switch moves from OFF state T0 to a transition period T1state. At this time, a small size driver C0 is turned ON, and thus, agate signal GSEN of a power switch slowly starts moving from Lo to Hi.In the midway, an increase in gate electrodes appears to be temporarilystopped in order to charge a mirror capacitance between a gate and adrain of a power switch. However, charging of VSSM completes in thisduration, and subsequently, there is no danger that an inrush current isgenerated.

In switching between a small size driver and a large size driver, aSchmidt trigger driver receives GSET that is a node at the most distalend side of a gate signal G of a power switch, and switches the nodewhen a logical threshold value of that Schmidt trigger driver has beenexceeded. At this time, a state of the power switch moves to a T2 state,and a large side driver C1 is driven. SENS90VCC senses this voltagelevel of GSEN. SENS90VCC detects that a level of G is obtained as 90%VCC, for example, stops a SENS90VCC circuit, and transmits C90VCC toFSM. Having received C90VCC, the FSM moves a current state to a T3 stateimmediately, and transmits the result to CLG. The CLG transmits an ACKsignal upon the receipt of the result.

This power switch controller also has a control signal of a micro I/O.The control signal of this micro I/O circuit carries out a control forchanging CDNMIO from Lo to Hi when a gate signal of the power switch hasexceeded a Schmidt logic threshold value VTH1. At this time, VSSM iscompletely 0V, and thus, a penetration current at the micro I/O does notflow. In this manner, in the case where ACK has been transmitted, themicro I/O can be already operable, thus making it possible to exchange asignal immediately.

Next, turning OFF the power switch will be described. First, REQ ischarged from Hi to Lo, whereby a power switch controller starts shutdowncontrol of the power switch. In this case, the power switch is turnedOFF by making a control for driving both gate signals of a small sizedriver and a large size driver to Lo. An ACK signal and CDNMIO arecontrol that, at a time point at which REQ has been entered, whereincontrol is carried out such that Lo is set, and having received REQ, apower switch is turned OFF immediately, thereby disabling its use.

A method for controlling a power switch controller has been describedabove. It is indispensable to actually mount a power switch on an LSIand to evaluate the characteristics in order to improve product quality.When a power switch is integrated on an LSI, the most noticeable pointis to grasp a voltage drop phenomenon of a peripheral circuit caused byan inrush current when turning ON the power switch, and a voltage dropphenomenon caused by an ON resistance of a power switch, which dependson a size of the power switch. Therefore, when an on-chip high precisionvoltage circuit is present, it becomes possible to select the size ofthe power switch and to obtain a proper size of a driver for driving thepower switch, based on the finding obtained by a test chip.

Thirteenth Embodiment

With reference to FIG. 26, a description will be given with respect to athirteenth embodiment relating to a semiconductor integrated circuitdevice according to the present invention.

FIGS. 26A and 26B are views showing an example of a voltage monitorcircuit for evaluating a fluctuation of a power voltage. This voltagemonitor circuit is composed of: a voltage monitor shown in FIG. 26A; anda monitor voltage amplifier circuit for amplifying an output signal of avoltage monitor shown in FIG. 26B.

First, a voltage monitor VMON shown in FIG. 26A will be described. Thiscircuit is designed by using two types of MISFETs having differentthreshold values. Here, a circuit in which a channel section of atransistor is blackened is a MISFET having a small threshold value. Thiscircuit is basically composed of a ring oscillator circuit, and operatesto deactivate or stop function in the case where no voltage ismonitored. This deactivating function is carried out by means of a NANDfunction. Namely, when a startup signal inversion signal “rngenb” of thering oscillator is set at Lo, the internal ring oscillator startsoperation. When “rngenb” is set at Hi, the internal ring oscillatorstops operation. This is achieved by a non-conjunction circuit NAND21.

A reason why a low threshold value type MISFET is used for the ringoscillator is that a MISFET has a good response property to convert afluctuation of a very small power voltage to an oscillation frequency ofthe ring oscillator with high precision. In addition, a MISFETs havingsmall threshold values are vertically stacked so that the oscillationfrequency of the ring oscillator is reduced.

An oscillation output signal “rngout” of a voltage monitor must passthrough a wiring having several millimeters between a point at which avoltage monitor is mounted and a monitor voltage amplifier VMONC, andthat load becomes very large. Thus, there is a danger that a signaldisappears partway in the wiring if a frequency is so high. An output ofthe ring oscillator is amplified by means of a buffer, and the amplifiedoutput is transmitted as “rngout” to the monitor voltage amplifier.

Next, a description will be given with respect to a monitor voltageamplifier circuit VMONC shown in FIG. 26B. This figure shows an exampleof controlling two voltage monitors VMON. This circuit comprised mainlya current mirror type amplifier circuit composed of a P-type MISFET, andselects whether or not an output from a voltage monitor is madeconductive by means of a transmission gate. In the case where the outputfrom the voltage monitor is conductive, the output is received by adrain of a P-type MISFET having a low threshold value, and a voltagemonitor output signal “vmon_out” is outputted with an amplification ratethat is determined depending on a gate width ratio between MP21 andMP22.

Although the embodiment has shown an example in which two VMONs havebeen connected to VMONC, a required number of select circuits andtransmission gates are added, and the added transmission gates areconnected to a drain of MP21, thereby making it possible to selectivelyremove and evaluate signals from a plurality of voltage monitors.

Fourteenth Embodiment

With reference to FIG. 27, a description will be given with respect to afourteenth embodiment relating to a semiconductor integrated circuitdevice according to the present invention.

FIG. 27 shows an example where constituent elements of a power supplyseparating area shown in FIG. 1 are mounted on a chip. The presentembodiment shows an example of a repeater circuit. FIG. 27 assumes AreaC, Area G, Area I, and Area H as regions in which a power switch isturned ON. In consideration of a power domain hierarchy shown in FIG. 1,these areas correspond to PDH1 to PDH3. Here, Area H is provided as oneof the subsidiary power domains that are allocated to be dispersed inpower domains. The areas in which the power switch is shut down are AreaA, Area B, Area D, Area E, and Area F. In consideration of the powerdomain hierarchy shown in FIG. 1, this case corresponds to a case inwhich power is shut down in PDH4.

First, let us consider a signal wiring sig1 to be transmitted to a padPAD1 from area D. In this case, sig1 must be passed through any of theupper layers of Area A, Area B, Area C, Area E, and Area F. Here, it isassumed that Area C, Area A, and Area B are passed. In this case, Area Cand Area D have a relationship that power supplies are independentlyshut down, and there is no power shutdown priority relationship betweenthese two power domains. Therefore, signal wiring sig11 from Area Dcannot be inputted to a circuit in Area C as it is. In a concept ofhierarchy described in FIG. 1, the above-described problem is avoidedvia Area H that falls into a “parent” in the upper hierarchy of Area Cand Area D. Thus, in FIG. 27, this sig11 is received in Area Hincorporated in Area C. The circuit receiving sig11 in this Area H is acircuit receiving a signal which first enters from a power shutdown areato a power applying area. Thus, this circuit must be an indefinitesignal propagation prevention circuit (μ I/O). Here, there is shown anexample of achieving a function with an AND function. In this example,propagation of an indefinite signal is blocked in the case where sig31is set at Lo after control has been carried out by means of a signal ofthe signal wiring sig31.

Now, a description will be given with respect to a signal of sig31. Thesignal of sig31 is a signal obtained when a signal of a μ I/O controlsignal wiring sig3 generated in Area I has been relayed by means of arepeater circuit mounted in Area H contained in Area E. There is apossibility that power is shut down when this control signal passesthrough Area E from Area I, thus making it necessary to relay thecontrol signal through a relay buffer circuit contained in a subsidiarypower domain Area H. This Area H is defined as a subsidiary powerdomain, and is mounted in Area C, Area A, and Area B. Thus, signals ofsig12, sig13, and sig14 may be relayed in a circuit contained in Area H.

Now, an example of sending out a signal from Area G to a pad PAD2 isshown. In this example, a repeater is provided in the same power supplyshut down area, and then, a signal is relayed in another power domain.In this case, it is assumed that Area E and Area F are passed. Whensignal wiring sig21 is relayed, a relationship between Area G and Area Efalls into one that Area G is a “parent” of Area E. If relaying iscarried out in Area E as it is in the case where power is shut down inArea E, signal transmission is disabled.

Therefore, this problem is avoided by mounting a relay circuit in asubsidiary power domain, i.e., Area H in which a relay buffer has beeninstalled in Area E. This circuit in Area H must be provided as a μ I/Ocircuit. This is because, even if power is shut down in Area G, powermay be continuously applied to Area H. This control of μ I/O is carriedout by control signal wiring sig4 from Area I. Then, an output signalfrom this μ I/O is relayed in Area H contained in Area F, and therelayed output signal is transmitted to PAD2.

In this way, a plurality of power domains is divided inside of an LSI(SoC). When these power domains have a power shutdown relationship witheach other as shown in FIG. 1, there is attained an advantageous effectthat a design of a repeater circuit is facilitated by using a subsidiarypower domain.

Fifteenth Embodiment

With reference to FIG. 28, a description will be given with respect to afifteenth embodiment relating to a semiconductor integrated circuitdevice according to the present invention.

FIG. 28 shows an example where constituent elements in the power supplyseparating area shown in FIG. 1 are mounted on a chip. The presentembodiment shows an example of mounting a clock buffer circuit of FIG.28 assuming that Area C, Area G, Area I, and Area H are areas in which apower switch is turned ON. In consideration of the power domainhierarchy shown in FIG. 1, these areas correspond to PDH1 to PDH3. Here,Area H is provided as one of the subsidiary power domains allocated tobe dispersed in power domains. Areas in which a power switch is shutdown are Area A, Area B, Area D, Area E, and Area F. In consideration ofthe power domain hierarchy shown in FIG. 1, this case corresponds to acase in which power is shut down in PDH4.

It is general that a clock signal is first outputted from a clock pulsegenerator CPG, and then, the outputted clock signal is distributed to awhole chip via relay buffers located at a plurality of stages. This CPGmust be installed in an area in which a frequency of carrying out thepower shutdown is low. The present embodiment assumes that this CPG ismounted in the highest hierarchy, i.e., Area I, in the hierarchy ofpower domains shown in FIG. 1. A clock signal from CPG contained in AreaI is temporarily wired to the center of a chip because there is a needfor adjusting a skew in equal length wiring or the like. In this case,FIG. 28 shows an example of wiring a signal to Area E through Area G. Inthis Area G, power is shut down independently of a group of Area A, AreaB, and Area C, thus making it impossible to relay a clock signal in thisArea G.

Therefore, when Area H is used as a subsidiary power domain, therelaying of a clock signal is carried out using a clock buffer installedtherein. A clock system signal wiring CK2 distributed to Area E is usedfor clock distribution into Area E, and clock distribution into otherpower domains must be carried out. In FIG. 28, a clock buffer in Area Eis used for a clock distributed into Area E, and a clock is distributedinto any other areas by using a clock buffer contained in Area H ofsubsidiary power domain. Clock system signal wirings CK3, CK4, and CK5are distributed in this manner.

CK3 is a signal to be distributed from the inside of Area E to theinside of Area F. This signal further assumes clock distribution intoArea D. Therefore, this signal is provided as a clock of a clock systemsignal wiring CK7 via a clock buffer contained in a subsidiary powerdomain Area H, installed in Area F. CK7 may be passed through a clockbuffer in Area F as a circuit for receiving a signal distributed intoArea F. With respect to the clock distributed into Area D as well,clocks may be further distributed by using a clock buffer installed inArea D in the case where the clocks in Area D and subsequent are notdistributed into any other power domain.

CK4 is a signal distributed from the inside of Area E to the inside ofArea C. Clocks may be further distributed by using a clock bufferinstalled in Area C in the case where the clocks in Area C andsubsequent are not distributed into any other power domain.

CK5 is a signal distributed from the inside of Area E to the insides ofArea B and Area G. A clock signal distributed into Area G is relayed viaa clock buffer contained in Area G, and the relayed signal isdistributed into Area G. On the other hand, a clock signal distributedinto Area B is provided as a clock of a clock system signal wiring CK6via a clock buffer contained in a subsidiary power domain, i.e., Area H,installed in Area B, because clock distribution from Area B into Area Ais further considered. CK6 may be passed through a clock buffer in AreaB as a circuit for receiving a signal distributed into Area B. Clocksdistributed into Area A may be further distributed by using a clockbuffer installed in Area A in the case where the clocks in Area A andsubsequent are not distributed into any other power domain.

In this manner, a plurality of power domains are divided inside of anLSI (SoC). In the case where these areas have a power shutdownrelationship with each other as shown in FIG. 1, there is attained anadvantageous effect that a design of a clock distributing circuit isfacilitated by using a subsidiary power domain.

The invention made by the Inventor has been specifically described abovewith reference to the embodiments. The present invention is not limitedto the foregoing embodiments. Of course, various modifications can occurwithout departing from the spirit of the invention.

The present invention is directed to a semiconductor integrated circuit.In particular, the present invention is effectively applied to a systemLSI oriented to a cellular phone device or a microprocessor.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention is not limited to thespecific details and representative embodiments shown and describedherein. Accordingly, various modifications may be made without departingfrom the spirit or scope of the general inventive concept as defined bythe appended claims and their equivalents.

What is claimed is:
 1. A semiconductor integrated circuit device formedon one chip comprising: a first functional block connected to a firstpower supply line and a second power supply line; a second functionalblock connected to the first power supply line and a third power supplyline and communicating with the first functional block; a thirdfunctional block connected to the first power supply line and a fourthpower supply line and communicating with the first functional block; afirst power switch shutting down the first functional block from powersupply via the second power supply line; a second power switch shuttingdown the second functional block from power supply via the third powersupply line; and a third power switch shutting down the third functionalblock from power supply via the fourth power supply line, wherein thefirst functional block is shut down by the first power switch when thesecond and the third functional blocks are shut down.
 2. A semiconductorintegrated circuit device according to claim 1, wherein the firstfunctional block is laid out inside each of the second and thirdfunctional blocks.
 3. A semiconductor integrated circuit deviceaccording to claim 2, wherein the first power switch to shut down thefirst functional block in the second functional block and the firstpower switch to shut down the first functional block in the thirdfunctional block are provided independently.
 4. A semiconductorintegrated circuit device according to claim 3, further comprising: afirst power switch controller that controls the first power switch toshut down the first functional block in the second functional block; anda second power switch controller that controls the first power switch toshut down the first functional block in the third functional block.
 5. Asemiconductor integrated circuit device according to claim 2, whereinthe first power switch to shut down the first functional block in thesecond functional block is provided in common with the first powerswitch to shut down the first functional block in the third functionalblock.
 6. A semiconductor integrated circuit device according to claim5, further comprising a power switch controller, wherein the powerswitch controller controls the first power switch.
 7. A semiconductorintegrated circuit device according to claim 4, wherein a first voltageis supplied to the first power supply line and a second voltage issupplied to the second to fourth power supply lines.
 8. A semiconductorintegrated circuit device according to claim 7, wherein the firstvoltage is higher than the second voltage.
 9. A semiconductor integratedcircuit device according to claim 1, further comprising a fourthfunctional block connected to the first power supply line and a fifthpower supply line, wherein the fourth functional block is not shut down,and wherein the fourth functional block comprises a power switchcontroller that controls the first to third power switches.
 10. Asemiconductor integrated circuit device according to claim 4, whereineach of the first to third functional blocks comprises a first MISFET,wherein each of the first to third power switches and the first and thesecond power switch controllers comprises a second MISFET having largergate insulation film thickness than the first MISFET, wherein each ofthe first to third power switches further comprises a first switch and asecond switch, and wherein the first and second power switch controllersturn the first switch on first and turn the second switch on second,respectively.
 11. A semiconductor integrated circuit device according toclaim 5, further comprising a power switch controller, wherein each ofthe first to third functional blocks comprises a first MISFET, whereineach of the first to third power switches and the power switchcontroller comprises a second MISFET having larger gate insulation filmthickness than the first MISFET, wherein each of the first to thirdpower switches further comprise a first switch and a second switch, andwherein the power switch controller turns the first switch on first andturns the second switch on second.
 12. A semiconductor integratedcircuit device according to claim 10, wherein each of the first andsecond power switch controllers comprise: means to detect whether avoltage of a virtual power supply line reaches a voltage level in whichthe corresponding functional block can operate; and a sensor circuit todetect the voltage of the virtual power supply, and wherein the firstand second power switch controllers control the first and the secondswitches, respectively.
 13. A semiconductor integrated circuit deviceaccording to claim 11, wherein the power switch controller comprises:means to detect whether a voltage of a virtual power supply line reachesa voltage level in which the first functional block can operate; and asensor circuit to detect the voltage of the virtual power supply, andwherein the power switch controller controls both the first and thesecond switches.
 14. A semiconductor integrated circuit device accordingto claim 10, wherein each of the first and second power switchcontrollers further comprises a sensor circuit that detects a voltage ofa gate of the second MISFET to control each of the first and secondswitches, and wherein each of the first and second power switchcontrollers compares the voltage of the gate of the second MISFET with apredetermined voltage level, and determines whether each of the firstand second switches is on or not.
 15. A semiconductor integrated circuitdevice according to claim 11, wherein the power switch controllerfurther comprises a sensor circuit that detects a voltage of a gate ofthe second MISFET to control each of the first and second switches, andwherein the power switch controller compares the voltage of the gate ofthe second MISFET with a predetermined voltage level, and determineswhether each of the first and the second switches is on or not.
 16. Asemiconductor integrated circuit device according to claim 12, whereineach of the first and second power switch controllers further comprisesa clock generator, and wherein the sensor circuit includes a dynamiccomparator that detects the voltage synchronized with a clock signalgenerated by the clock generator.
 17. A semiconductor integrated circuitdevice according to claim 13, wherein the power switch controllerfurther comprises a clock generator, and wherein the sensor circuitincludes a dynamic comparator that detects the voltage synchronized witha clock signal generated by the clock generator.